On Wed, Sep 28, 2016 at 3:30 PM, Scott Stobbe <[email protected]> wrote: > You are certainly no where near -40 dBm into 50 ohms as the blog Bryan > posted above. Your setup may have 70-80 pF of load (~220 Ohms), if you also > measured the output voltage with a 10x probe you could work backwards to > see how close you are to 50 Ohms output. > > Roughly speaking it sounds like it will be in spec for amplitude, but to > definitive you will have to load it with 50 Ohms as others have suggested. > Anything can work plug your bnc cable into a 50 Ohm input instrument (even > if its ancient) and measure the output voltage on the OCXO with a 10X > probe. Or a near enough to 50 Ohm resistor as Tim suggested.
I obtained a (Pomona I think) 50 Ohm terminator/6db attenuator and repeated the measurements with the MV89A, connecting the RF and GND pins through a BNC cable and the terminator directly into the Channel 1 of the scope . I now get an amplitude on the scope FFT of -6.99 dB measured with the cursors. According to the scope manual this is referenced to 1 V rms so this would give a Vrms equivalent to -0.99 dB i.e. 0.89 Volts. Assuming I've done the rest of the maths conversions right, this would give a peak-to-peak value of 1.26 V and a power of ~11 dBm. (Assuming everything worked alright, I put the scope captures up on our Owncloud at https://cloud.lcogt.net/index.php/s/pHBV6EORT33ucjA - Channel 1 is the MV89A, Channel 2 is the GPSDO output) So I think this means my unit is behaving OK ? Cheers, Tim _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
